Multiple turn mechanism for manual lumbar support adjustment

ABSTRACT

An actuator is disclosed. The actuator includes: an output gear, a pinion, a drive shaft, a housing, and a spring. The output gear is adapted to receive a traction element. The pinion is in driving communication with the output gear. The drive shaft is interconnected with the pinion. The housing is adapted to receive the output gear and the drive shaft. The coil spring is circumjacent the drive shaft and located in a position intermediate the drive shaft and the housing, whereby rotation of the drive shaft causes the coil spring to frictionally disengage from the housing such that the output gear may rotate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. application Ser. No. 11/042,648filed Jan. 25, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to actuators and, more particularly, toa transmission improvement for an actuator.

2. Related Art

Many mechanical devices need to be moved to a user selected position andthen held there against a force that is biased to return the device toits original position. Such devices are commonly used for ergonomicsupports in seating, especially lumbar supports for automobile seats.Lumbar supports exert a comfortable force against the lumbar spine of aseat occupant. This force is applied mechanically through a wide varietyof configurations including arching, bending, tightening, extending orotherwise moving a pressure surface. Pressure surfaces are of an equallywide variety including straps, paddles, “baskets,” arching surfaces,bowed surfaces and so forth. These devices must allow the user to selecta desired position for the pressure surface, and thereafter hold thatposition after the user has released whatever device and linkage hasbeen used to move the pressure surface to the selected position. Thelinkages are of a wide variety including rods, levers, springs, cables,and especially coaxial traction cables such as Bowden cables. Thelinkage, for example a Bowden cable, has a connection to the lumbarsupport at one end and a connection to an actuator at the other end. Theactuator is positioned where the user may operate it, typically at theedge of the seat.

There is a great variety of actuator structures used for these purposes,both mechanical and electrical. They share in common the function ofmoving the pressure surface to a selected position, and then holding thepressure surface in that position against a force exerted by the seatoccupant's weight. That force is biased towards returning the pressuresurface to its original position, which is usually flat. The most commonlinkage, the Bowden cable, has a flexible conduit, also called a“sleeve” or “sheath,” through which runs a coaxially sliding wire.Actuators have a seat for the end of the sleeve and seat for the end ofthe wire. The opposite ends of the wire and sleeve are connected todifferent portions of the lumbar or other ergonomic support, such thatpulling the wire through the sleeve moves the pressure surface to thedesired position. Accordingly, the most commonly used actuators aredesigned to pull a Bowden cable wire through a Bowden cable sleeve. Theactuators must exert the force necessary to pull the wire through thesleeve to actuate the lumbar support. They must also hold the wireagainst the return force of the passenger's weight on the lumbar supportpulling the wire back into the sleeve. In addition the actuators mustalso be able to release the holding force from the wire so that the usermay return the ergonomic device to its original position or to anotherselected position.

Actuators achieve these necessary functions of movement, holding andrelease through a variety of mechanisms. Electronically poweredactuators frequently use gears connected to take up wheels or drums forpulling the Bowden cable wire. Manual actuators may also use gears andtake up drums, but more typically include a brake, ratchet or clutch.Brakes, ratchets and clutches are powered by levers or hand wheelsturned by the users hand.

There remains a continuing need in the art for reducing the size and theprofile of the assembled actuator. There also remains a continuing needin the art for easing and streamlining assembly of the component partsof the actuator. Finally, there is a continuing need to reduce thenumber, and consequently the expense, of the components to be assembledinto actuators.

SUMMARY OF THE INVENTION

The invention is an actuator having an output gear, a pinion, a driveshaft, a housing, and a spring. The output gear is adapted to receive atraction element. The pinion is in driving communication with the outputgear, and the drive shaft is interconnected with the pinion. The housingis adapted to receive the output gear and the drive shaft.

The spring is circumjacent the drive shaft and located in a positionintermediate the drive shaft and the housing. In a static state, thespring frictionally engages the housing to prevent rotation of the driveshaft. Because the pinion is connected to the drive shaft, the springalso prevents rotation of the pinion. Moreover, due to the engagement ofthe pinion with the output gear, the spring also prevents rotation ofthe output gear. However, when a dynamic force is applied to the driveshaft, such as when the drive shaft is rotated via a knob or lever, thespring is disengaged, thereby allowing rotation of the drive shaft, and,thus, the pinion and the output gear. Because the spring imparts only anominal stress on the housing and the drive shaft, it is possible tomake the housing and the drive shaft from plastic.

The actuator may be used to operate an ergonomic device, such as alumbar support. As an example, the output gear may be rotated to draw orcompress a traction element for adjustment of the ergonomic device. Whena dynamic force is applied to the drive shaft, the spring frictionallydisengages from the housing to allow rotation of the output gear, andthus movement of the traction element. When the dynamic force isreleased, the spring frictionally engages the housing such that theoutput gear is locked in position, thereby preventing further movementof the traction element.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of an ergonomic device with an actuator ofthe present invention attached;

FIG. 2 is a perspective view of an actuator in a first embodiment;

FIG. 3 is an exploded view of the first embodiment;

FIG. 4A is a perspective view of the assembled drive shaft and pinion;

FIG. 4B is a perspective view of the assembled drive shaft, pinion andspring;

FIG. 4C is a perspective view of the assembled drive shaft, pinion andspring;

FIG. 5 is a top view of the first embodiment;

FIG. 6 is a sectional view of the actuator taken along line 6-6 in FIG.5;

FIG. 7 is a sectional view of the actuator taken along line 7-7 in FIG.5;

FIG. 8 is a bottom view of the actuator housing in the first embodiment;

FIG. 9 is a perspective view of the actuator in a second embodiment; and

FIG. 10 is an exploded view of the second embodiment.

DETAILED DESCRIPTION OF THE PREFEREED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

FIG. 1 illustrates a typical ergonomic device. In the depictedembodiment, the ergonomic device is a lumbar support 100 with anactuator 10 of the present invention installed. The lumbar support 100has a fixed portion 110 and an arching portion 112. The arching portion112 slides upon guide rails 114, which may be attached to a seat frame(not shown).

The arching portion 112 is moved via a traction device. In the depictedembodiment, the traction device is a bowden cable 116. The bowden cable116 is comprised of an outer, flexible sleeve 122, which retains anddirects a wire 124 (best seen in FIG. 5) within the sleeve which canslide co-axially in and out of the sleeve. A first end 118 of the bowdencable 116 is attached to the arching portion 112, and a second end 120is attached to the actuator 10. The actuator 10 applies traction to thebowden cable wire 124 when a seat occupant rotates a knob 50. The knob50 may alternatively be a lever or other device giving mechanicaladvantage. This tractive force draws the bowden cable wire 124 throughthe bowden cable sleeve 122 causing the arching portion 112 to movealong the guide rails 114, whereby the arching portion 112 bowsoutwardly to provide a lumbar supporting arch.

Hence, it is apparent that the most rudimentary function of any actuatoris to draw the bowden cable wire 124 through the bowden cable sleeve 122for operation of the ergonomic device. If an alternative traction devicewere elected as a design choice, the most rudimentary function of theactuator would remain to draw the tractive device, whether it is a rod,cable, or otherwise, in a direction applying tractive force to actuatethe ergonomic device. The present invention may be applied to any suchtractive devices. In another alternative design choice, compressivepressure may be used to bow an archable surface. The present inventionmay likewise be used to drive such a compressive mechanism.

FIGS. 2-8 illustrate a first embodiment of the actuator 10. The actuator10 includes a housing 12, a cap 14, a pinion 16, a drive shaft 18, anoutput gear 20, a gear shaft 22, and a spring 24. In some embodiments,the housing 12 includes a plurality of mounting ears 13. As examplesonly, the housing 12 and the drive shaft 18 may be made of plastic,whereas the cap 14, the pinion 16, and the output gear 20 may all bemade of metal. Those skilled in the art, however, will understand thatall of the components could be made of metal. The cap 14 is adapted formounting to the housing 12. In the depicted embodiment, the cap 14includes rib stiffeners 54 to add rigidity to the cap 14.

As best seen in FIG. 3, the pinion 16 has a locking portion 30, a gearedportion 32, and a bearing portion 34. The locking portion 30 is designedto inter-lock with an inner portion 31 (best seen in FIG. 7) of thedrive shaft 18. While in the depicted embodiment the locking portion 30is keyhole-shaped, other shapes may be used. What is significant is thatthe pinion 16 inter-locks with the drive shaft 18 such that the pinion16 and the drive shaft 18 rotate together. Moreover, in someembodiments, the pinion 16 and the drive shaft 18 may be configured asone piece.

The geared portion 32 mates with the output gear 20. In the depictedembodiment, the geared portion 32 has first gear teeth 26 that mesh withsecond gear teeth 28 of the output gear 20. A lubricant (not shown),such as grease, may be applied to the first gear teeth 26 and the secondgear teeth 28 in some embodiments. While gear teeth are used in thedepicted embodiment to mate the pinion 16 and the output gear 20, othersimilar features may be used. What is important is that the pinion 16and the output gear 20 are locked together so that they cannot rotateindependently of one another. It is important to note that thearrangement of the pinion 16 and the output gear 20 provide an effectivegear reduction. In the depicted embodiment, the pinion 16 rotates about4.5 times for each revolution of the output gear 20. In this manner, ahigh speed but low torque rotation of the pinion 16 may be used torotate the output gear 20.

The bearing portion 34 supports the pinion 16. In the depictedembodiment, the bearing portion 34 has a cylindrical shape. The bearingportion 34 is received by a first void 37 in the cap 14. In someembodiments, lubricant, such as grease, may be applied to the first void37 to reduce friction between the cap 14 and the bearing portion 34.Thus, the pinion 16 and the drive shaft 18 rotate about the first void37 and the bearing portion 34.

The output gear, or pulley, 20 rotates about the gear shaft 22, which isaffixed to the housing 12 and the cap 14. Lubricant, such as grease, maybe applied to the gear shaft 22 in some embodiments. In the depictedembodiment, the housing 12 and the cap 14 each have a second void 35that receive a respective end of the gear shaft 22. Thus, the gear shaft22 is captured between the housing 12 and the cap 14. In the depictedembodiment, the gear shaft 22 has a diameter of 5 mm. The output gear 20depicted in FIG. 3 includes a recess 33 and a stop 21 located in therecess 33. The stop 21 extends radially from the center of the outputgear 20. The stop 21 and the recess 33 are explained in greater detailbelow. In the preferred embodiment, the output gear 20 further consistsof a recess or a channel 44 centrally located on the radial surface ofthe gear. The channel 44 serves as a mount for seating the bowden cablewire 124.

The drive shaft 18 rotates within the housing 12 and slides over thepinion 16, thereby engaging it. The drive shaft 18 includes a mountingsurface 29. A device providing mechanical advantage may be mounted tothe mounting surface 29. As an example, the knob 50 may be mounted tothe mounting surface 29, and a user may rotate the drive shaft 18 viathe knob 50. The drive shaft 18 has a first shoulder 23 and a guidesurface 27. The drive shaft 18 also includes a second shoulder 51. Asbest seen in FIG. 6, the second shoulder 51 locates the drive shaft 18relative to the housing 12.

The spring 24 is located intermediate the drive shaft 18 and the housing12. In other words, the spring 24 lies circumjacent the drive shaft 18and adjacent the housing 12. In the depicted embodiments, the spring 24lies over the guide surface 27 and rests upon the first shoulder 23. Thespring 24 selectively engages an inner surface 52 (best seen in FIG. 7)of the housing 12. The diameter of the spring 24 is such that it has apress fit with the housing 12. In a static state, the spring 24frictionally engages the housing 12 to prevent rotation of the driveshaft 18. Because the pinion 16 is connected to the drive shaft 18, thespring 24 also prevents rotation of the pinion 16. Moreover, due to theengagement of the pinion 16 with the output gear 20, the spring 24 alsoprevents rotation of the output gear 20. Significantly, due to the gearreduction arrangement of the pinion 16 and the output gear 20, only asmall braking torque by the spring 24 is required to brake the pinion 16and, thus, the output gear 20.

In a dynamic state, the spring 24 is frictionally disengaged from thehousing, thereby allowing rotation of the drive shaft 18, and, thus, thepinion 16 and the output gear 20. Because the spring imparts only adistributed nominal stress on the housing 12 and because the pinion 16requires a small braking torque, it is possible to make the housing 12from plastic, thereby reducing the overall cost of the actuator 10.

FIGS. 4A, 4B and 4C illustrate the assembled pinion 16 and the driveshaft 18. FIG. 4A illustrates only the pinion 16 and the drive shaft 18.FIGS. 4B and 4C illustrate the pinion 16, the drive shaft 18, and thespring 24 as assembled. The drive shaft 18 includes a cut out 19 toreceive the pinion 16. When the pinion 16 is assembled with the driveshaft 18, there is provided a first gap 72 and second gap 74. A firsttab 60 and a second tab 62 of the spring 24 ride in the respective gaps72, 74.

The drive shaft 18 includes a first face 64 and a second face 66.Similarly, the pinion 16 includes a third face 68 and a fourth face 70.The tabs 60, 62 ride on the faces 64, 66, 68, 70 to either expand orcollapse the spring 24. In a first example, the drive shaft 18 may berotated in a first direction such that the second face 66 contacts thesecond tab 62 and moves the tab 62 in the first direction to reduce thediameter of the spring 24. In a second example, the pinion 16 may berotated in a second direction due to a force being applied to the outputgear 20 by the bowden cable 116. When the pinion 16 is rotated in thesecond direction, the fourth face 70 of the pinion 16 contacts thesecond tab 62 and moves the second tab 62 in the second direction suchthat the diameter of the spring 24 is increased. By increasing thediameter of the spring 24, the amount of pressure exerted by the spring24 on the housing 12 is increased, thereby increasing the frictionbetween the two surfaces. As such, the pinion 16 is effectively braked.

Referring now to FIG. 5, the bowden cable 116 is assembled to theactuator 10. The actuator 10 includes a first channel 46 and a secondchannel 48. In the depicted embodiment, the first channel 46 is co-axialwith the second channel 48 but other configurations may be used. Eachchannel 46, 48 has a passageway 36 and a slot 38 (as best seen in FIG.2). In some embodiments, the channels 46, 48 may be counter-bored tofacilitate reception of the cable sleeve 122. The corresponding oppositefirst channel 46 and second channel 48 allow for reverse installation ofa bowden cable wire 124 so that the actuator 10 may be installed foractuating either clockwise traction or counterclockwise traction inorder to accommodate seat design flexibility such as would be useful ininstalling mirror image actuators on outboard sides of both a driver'sand a passenger's side seat.

The output gear 20 has a notch 42 for receiving installation of thebowden cable wire end stop 126. The bowden cable wire 124 would then bewrapped partially around the output gear 20 and lead out through one ofthe passageways 36. The output gear 20 may include a feature to receivethe bowden cable wire 124. For example, the output gear 20 may have agroove 44 to receive the bowden cable wire 124. In this configuration,rotation of the output gear 20 wraps the bowden cable wire 124 furtheraround the output gear 20 which effects a shortening of the bowden cablewire 124 at the opposite end of the bowden cable 116. This shorteningalso draws the bowden cable wire 124 through the bowden cable sleeve 122applying the desired traction to the ergonomic device to which the otherend of the bowden cable wire 124 and bowden cable sleeve 122 areattached.

The actuator 10 also includes an opening 40. To assemble the bowdencable 116 to the actuator 10, the bowden cable wire end stop 126 isplaced through the opening 40 and into the notch 42. The bowden cablewire 124 is then pulled through the slot 38 until the bowden cablesleeve 122 is beyond the end of the first channel 46 or the secondchannel 48. The bowden cable sleeve 122 is then placed within thepassageway 36 until it contacts a wall 56 (best seen in FIG. 6).

FIG. 8 illustrates a bottom view of the housing 12. In the embodimentdepicted in FIG. 8, the housing includes a first face 15 and a secondface 17. The faces 15, 17 may be mounted on the housing 12, but in thedepicted embodiment, the faces 15, 17 are integral with the housing 12.The faces 15, 17 are explained in greater detail below.

FIG. 9 illustrates a second embodiment of the actuator 10. The secondembodiment is very similar to the first embodiment except for thearrangement of the first channel 46 and the second channel 48. In theembodiment depicted in FIG. 9, the first channel 46 is parallel to thesecond channel 48. To accommodate this configuration, the actuator 10includes two openings 40, one opposite the other and corresponding witheach channel 46, 48.

Typically, the actuator 10 is used to limit the operation of theergonomic device. For example, if the ergonomic device is a lumbarsupport, then the actuator 10 may be used to limit the travel of thelumbar support to prevent its over travel. This may be accomplished inseveral ways. For example, as best seen in FIG. 10, the output gear 20may include a non-geared portion 80. When the pinion 16 rotates,eventually it will encounter the non-geared portion 80. Because thenon-geared portion 80 does not include gear teeth, the pinion 16 willnot mesh with the output gear 20 in this location. As such, the pinion16 will prevent further rotation of the output gear 20, and, thus,prevent further movement of the bowden cable wire 124. As those skilledin the art will understand, the movement of the ergonomic device isdirectly related to the movement of the traction element, such as thebowden cable. Therefore, by controlling the width and location of thenon-geared portion 80, it is possible to limit the movement of theergonomic device.

Alternatively, and referring once again to FIGS. 2-8, the housing 12 mayinclude the first face 15 and the second face 17. The first face 15 andthe second face 17 ride in the recess 33 of the output gear 20. The stop21 located in the recess 33 limits the rotation of the output gear 20relative to the first face 15 or the second face 17. In other words, theoutput gear 20 may rotate in either a first direction until the stop 21engages the first face 15, or the output gear 20 may rotate in a seconddirection until the stop 21 engages the second face 17. As an example,the pinion 16 may rotate the output gear 20 in a first direction untilthe stop 21 engages the first face 15 of the housing 12. As such, thefirst face 15 will prevent further rotation of the output gear 20, and,thus, prevent further movement of the bowden cable wire 124. As thoseskilled in the art will understand, the movement of the ergonomic deviceis directly related to the movement of the traction element, such as thebowden cable. Therefore, by controlling the location of the first face15, the second face 17, and the stop 21, it is possible to limit themovement of the ergonomic device.

The actuator 10 is assembled by providing a housing, placing a springover a drive shaft, inserting the spring and the drive shaft into thehousing, interlocking a pinion with the drive shaft, inserting a gearshaft into the housing, and placing a drive gear onto the gear shaft andin a driven relationship with the pinion. In some embodiments, anoptional step is mounting a cap to the housing. A further step may be toplace a tab of the spring within a gap located between the pinion andthe drive shaft.

As various modifications could be made to the exemplary embodiments, asdescribed above with reference to the corresponding illustrations,without departing from the scope of the invention, it is intended thatall matter contained in the foregoing description and shown in theaccompanying drawings shall be interpreted as illustrative rather thanlimiting. Thus, the breadth and scope of the present invention shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims appendedhereto and their equivalents.

1. A traction cable brake for an ergonomic device adapted formaintaining a position against a load, the load presenting to the brakeas traction on a traction cable; said traction cable brake comprising: agear having a channel, which is located centrally with respect to a topand bottom surface of said gear, wherein said channel functions as amount for seating a traction cable wire, said wire, when under a load,biasing said gear in a first rotational direction; said gear having anotch for receiving installation of an end stop of the traction cablewire; a housing, said gear being mounted in said housing; a drive shaftadapted to receive rotational force from a handle; said drive shaftbeing operatively engaged with said gear, said operative engagementtransferring a force on said drive shaft to turn said gear in said firstrotational direction or in a second rotational direction; a spring, saidspring having a first extension and second extension; a guide surface,said guide surface being dimensioned to receive said spring on an outersurface thereof; an inner surface on said housing; wherein said driveshaft has a circumferential shoulder having a first face and a secondface, the first and second faces being radially disposed; a third andfourth face, said third and fourth face being in operative engagementwith said gear; wherein said first, second, third and fourth faces aresituated with respect to said first and second extensions such that whena moment is not applied to said drive shaft said first, second, thirdand fourth faces are moved such that said spring is moved to a firstdiameter, and such that, when said moment is applied to said driveshaft, said first, second, third and fourth faces are moved such thatsaid spring is moved to a second diameter; wherein said springfrictionally engages with said inner surface when said spring is movedto said first diameter, and wherein said spring disengages with saidinner surface when said spring is moved to said second diameter; whereinsaid gear is prevented from rotating when said spring is engaged withsaid inner surface; and wherein, said wire is used to actuate anergonomic device.
 2. The brake of claim 1 further comprising a stop,said stop establishing a rotation limit for said drive shaft.
 3. Thebrake of claim 2 wherein said stop is integrally formed in said housing.4. The brake of claim 1 further comprising a stop, said stopestablishing a rotation limit for said gear.
 5. The brake of claim 4wherein said stop is integrally formed with a portion of said gear. 6.The brake of claim 1 further comprising an integrally formed component,a portion of said integrally formed component comprising said driveshaft and a separate portion of said integrally formed componentcomprising said first face.
 7. The brake of claim 6 wherein saidintegrally formed component includes a portion comprising said secondface.
 8. The brake of claim 1 including an integrally formed component,a portion of said integrally formed component comprising said driveshaft and another portion of said integrally formed component comprisingsaid third and fourth faces.
 9. The brake of claim 1 further comprisinga stop integrally formed in said gear, said stop operatively engagingone of a first stopping face and a second stopping face integrallyformed on said housing to establish a rotational limit for said gear.10. The brake of claim 1 wherein said spring is a coil spring.
 11. Anactuator for an ergonomic support for a seat comprising: a spring havinga first extension and a second extension, said spring being capable ofmoving from a first diameter to a second diameter when a force isapplied to said first and second extensions; a guide surface, said guidesurface being dimensioned to receive said spring on an outer surfacethereof such that said spring may rotate relative to said guide surfaceand said guide surface being dimensioned to lockingly engage said springwhen said spring is in said second diameter; a drive shaft disposed toengage said first extension of said spring such that when said driveshaft is rotated in a first direction, said spring is maintained in saidfirst diameter; a gear being in operative engagement with said driveshaft; said gear having a channel, which is located centrally withrespect to a top and bottom surface of said gear, wherein said channelfunctions as a mount for a traction cable wire; said gear having a notchfor receiving installation of an end stop of the traction cable wire;wherein said first extension of said spring and the drive shaft aresituated such that when said drive shaft is not rotated in said firstdirection and when a force is applied to said gear by said tractioncable wire said first extension of said spring is moved such that saidspring is moved to said second diameter; and a housing, said housingencapsulating said drive shaft, said spring, said guide surface and saidgear; wherein said traction cable wire is used to actuate an ergonomicdevice.
 12. The actuator of claim 11 wherein the drive shaft is disposedto engage said second extension of said spring such that when said driveshaft is rotated in a second direction, said spring is maintained insaid first diameter and said gear is rotated in said second direction.13. The brake of claim 11 wherein said spring is a coil spring.
 14. Atraction cable brake for an ergonomic device adapted for maintaining aposition against a load, the load presenting to the brake as traction ona traction cable; said traction cable brake comprising: a gear having achannel, which is located centrally with respect to a top and bottomsurface of said gear, wherein said channel functions as a mount forseating a traction cable wire, said wire, when under a load, biasingsaid gear in a first rotational direction; said gear having a notch forreceiving installation of an end stop of the traction cable wire; ahousing, said gear being mounted in said housing; a lever mount, saidlever mount being adapted for seating a lever; an drive shaft betweensaid lever mount and said gear, said drive shaft transferring a force onsaid lever mount to turn said gear in a said first rotational directionor in a second rotational direction; a coil spring, said coil springhaving a first tab and second tab and said coil spring having anunloaded diameter and a loaded diameter; a guide surface on said driveshaft, said guide surface being dimensioned to receive said coil spring,said guide surface having an outer surface; an inner surface on saidhousing; wherein said drive shaft has a circumferential shoulder havinga first face and a second face, the first and second faces beingradially disposed; a third and fourth face, said third and fourth facebeing in operative engagement with said gear; wherein said first,second, third and fourth faces are situated with respect to said firstand second extensions such that when a moment is not applied to saiddrive shaft said first, second, third and fourth faces are moved suchthat said spring is moved to a first diameter, and such that when saidmoment is applied to said drive shaft said first, second, third andfourth faces are moved such that said spring is moved to a seconddiameter; wherein said spring frictionally engages with said innersurface when said spring is moved to said first diameter, and whereinsaid spring disengages with said inner surface when said spring is movedto said second diameter; wherein said gear is prevented from rotatingwhen said spring is engaged with said inner surface; and wherein, saidwire is used to actuate an ergonomic device.